The present invention relates generally to material transfer devices, and in particular, to an articulated arm which is coaxially driven in to effect rotation and vertical movement of substrate holders used in material transfer devices used in the production of substrates which may take the form of semi-conductor wafers and or flat panels, or other substrates, or media.
The need for high throughput transport devices which can move a substrate or workpiece between remote locations within highly confined areas as defined by a limited footprint such as found in the manufacture of wafers or panels used in the semiconductor industry are in high demand. This is because in the process of manufacturing, not just in the semiconductor industry, the need to move a workpiece from one position to the next not only requires a high throughput rate, but also accuracy of repeatability of placement of workpieces in registration at predetermined orientations on a support surface. Still a further constraint is to fabricate a positioning machine which is capable of working in a clean room environment where the existence of particulates is minimized, if not nonexistent.
Attempts have been made to fabricate placement devices which employ rotary to linear motion robotic arms which can effect straight line movement of a substrate between stations. One such arm is disclosed in U.S. Pat. No. 4,897,015. In this patent, it is disclosed to provide an end effector which is capable of carrying a substrate such as a silicon wafer from one point to another in a straight line. This is accomplished by using a series of pulleys which drivingly connect two pivot linkages about which the articulated parts travel. The dual pulley system however introduces unwanted possibilities of error by having two nonpositively connected drives control movement of the end effector, each of which drives presents a separate possibility of error through the introduction of possible belt/pulley slippage. In the device disclosed in U.S. Pat. No. 4,897,015 the slippage problem is of a furthermore problematic because of the small width belts which are used to articulate the drive mechanism.
In copending U.S. patent application Ser. No. 08/679,845, filed on Jul. 15, 1996 and entitled BATCH LOADER ARM, there is disclosed an articulated arm which is driven between extended and retracted positions through the use of a rotary drive which is laterally offset from the Z-axis drive. While such a system has been successful, there are applications where it is more desirable to drive the articulate arm at the Z-axis thereby consolidating theta and Z-axis movements in a single drive.
Accordingly it is an object of the present invention to provide an article transfer mechanism for moving an article between first and second stations in a straight linear path with repeatability of movement and which mechanism is articulated by a drive which both rotates and vertically moves the mechanism about and along a given axis.
It is still a further object of the invention to provide a transport device of the aforementioned type wherein a substrate is capable of being moved as a group of stacked substrates from one position to the next or to effect greater throughput of the processing operation.
It is yet a further object of the invention to provide a transport mechanism of the aforementioned type wherein the mechanism provides a holder on which is stacked a plurality of substrates which are handled as a group and worked on by subsequent operations using the holder.
Still a further object of the invention is to provide a transport mechanism which is capable of functioning in a clean room environment.
Further objects and advantages of the present invention will become apparent from the following specification and appended claims.